1. Field of the Invention
This invention relates to a valve operating system for internal combustion engines, having a roller rolling contacting a valve-operating cam.
2. Description of the Prior Art
Such a valve operating system for internal combustion engines has already been known from Japanese Patent Laid-Open No. 13442/1999 and so on.
The known valve operating systems of this kind include a valve operating system disclosed in Japanese Patent Laid-Open No. 13442/1999. This is a roller-carrying rocker arm provided with an oil supply passage for supplying lubricating oil to a roller. However, with the development of a higher-revolution engine, a more sufficient lubrication of a roller has been demanded. Hitherto, the oil supply passage has been formed in a straight form by drilling. Therefore, in order to enlarge an oil supply port for the purpose of increasing an oil supply rate, it has also been necessary that the diameter of an oil supply passage be increased in accordance with the enlarged oil supply port. This causes a rocker arm to be enlarged, and in its return the internal combustion engine to be also enlarged. In the known valve operating system, a roller shaft has been fitted in a contacting state in a bottomed portion-carrying engagement bore of the rocker arm, so that it has been difficult to supply lubricating oil to the portion of a roller which is the most distant from a rocker arm supporting wall portion.
The present invention has been made in view of the above-mentioned circumstances, and provides a rocker arm which solves the above-mentioned problems encountered in the known art roller-carrying rocker arm, and which has a high lubricating ability with respect to a roller, a high durability and a long lifetime.
The inventors of the present invention have assiduously studied so as to attain the objects above, and, as a result, have unexpectedly found improved techniques concerning the valve operating system of this kind. A valve operating system for internal combustion engines of our present invention has a rocker arm support member provided with an oil passage in an inner portion thereof, a cam shaft provided on a valve operating cam, and an oil supply passage which is provided in the rocker arm having a roller contacting the valve operating cam while the cam""s rolling, and which is used to supply lubricating oil from the rocker arm support member to the roller, in which system a sectional area of a flow passage of the oil supply passage is increased gradually from an opening thereof on the side of the roller toward an opening thereof on the side of the rocker arm support member.
The inventors of the present invention have also surprisingly discovered the additional techniques capable of ideally improving the lubricating ability of the system of this kind with respect to the mentioned roller. A valve operating system for internal combustion engines which utilizes these techniques has a rocker arm support member provided with an oil passage in an inner portion thereof, a cam shaft provided with a valve operating cam thereon, a roller shaft provided on an outer circumference thereof with a roller contacting the cam while the cam""s rolling via a needle bearing, and a rocker arm provided with first and second support wall portions mutually separated each other with a space and opposed to each other, the first support wall portion being provided with a bottomed portion-carrying engagement bore, the roller shaft being inserted in the engagement bore, the rocker arm in the engagement bore being provided therein with an oil supply passage for supplying lubricating oil from the rocker arm support member to the engagement bore, the system including a clearance provided between the end portion of the roller shaft which is most distant from the rocker arm support member and the bottomed portion.
Moreover, the rocker arm can be manufactured industrially with ease by using a well known method, for example, a lost wax process, the MIM process or die casting and so on.
The present invention relates to a valve operating system for internal combustion engines, having a roller rolling contacting a valve operating cam, the system being provided with an oil supply passage capable of reducing a pressure loss to a low level even when a flow rate of lubricating oil entering the oil supply passage increases in accordance with a heightened engine speed, improving the lubricating ability with respect to the roller, and attaining a long lifetime of a rocker arm. This valve operating system includes a rocker arm support member provided with an oil passage in an inner portion thereof, a cam shaft provided on a valve operating cam, and a rocker arm which is provided with a roller rolling contacting the valve operating cam, and which is provided in an inner portion thereof with an oil supply passage for supplying lubricating oil from the rocker arm support member to the roller, the sectional area of the flow passage of the oil supply passage increasing gradually from an opening thereof on the side of the roller toward an opening thereof on the side of the rocker arm support member.
More concretely to say:
(1) According to an aspect of the present invention, the present invention provides the valve operating system for internal combustion engines comprising a rocker arm support member provided with an oil passage in an inner portion thereof, a cam shaft provided with a valve operating cam thereon, and a rocker arm which is provided thereon with a roller contacting the valve operating cam while the cam""s rolling, and which is provided in an inner portion thereof with an oil supply passage for supplying a lubricating oil from the rocker arm support member to the roller, wherein the valve operating system is characterized by that the sectional area of a flow passage of the oil supply passage increases gradually from an opening thereof on the side of the roller toward an opening thereof on the side of the rocker arm support member.
(2) According to another aspect of the present invention, the present invention provides a valve operating system for internal combustion engines in accordance with the first invention (1) above, in which the oil supply passage extends linearly at the portion thereof which is on the side of an outer circumference of the rocker arm in the direction in which the oil supply passage crosses the cam shaft at right angles thereto, and increases in the sectional area of the flow passage thereof at the portion thereof which is on the side of the roller toward the side of the roller as the oil supply passage extends toward the rocker arm support member.
(3) According to still another aspect of the present invention, the present invention provides a valve operating system for internal combustion engines having a rocker arm support member provided with an oil passage in an inner portion thereof, a cam shaft provided with a valve operating cam thereon, a roller shaft provided on an outer circumference thereof with a roller contacting the valve operating cam via a needle bearing while rolling, and a rocker arm provided with first and second support wall portions mutually spaced each other and opposed to each other, the first support wall portion having a bottomed portion-carrying engagement bore, the roller shaft being inserted in the engagement bore, the rocker arm being provided in an inner portion thereof with an oil supply passage for supplying a lubricating oil from the rocker arm support member to the engagement bore, wherein the valve operating system is characterized by that a clearance is provided between the end portion of the roller shaft which is most distant from the rocker arm support member and the bottomed portion.
(4) According to a further aspect of the present invention, the present invention provides a valve operating system for internal combustion engines in accordance with the third invention (3) above, in which the roller shaft is fixed to the second support wall portion by a snap ring, the width of the clearance being larger than that of the snap ring.
(5) According to another aspect of the present invention, the present invention provides a valve operating system for internal combustion engines in accordance with any of the first to fourth inventions (1) to (4) above, in which the rocker arm is manufactured by a lost wax process.
(6) According to a further aspect of the present invention, the present invention provides a valve operating system for internal combustion engines in accordance with the above (1) or (2), wherein the rocker arm is manufactured by a lost wax process.
(7) According to a further aspect of the present invention, the present invention provides a valve operating system for internal combustion engines in accordance with the above (3) or (4), wherein the rocker arm is manufactured by a lost wax process.